Survivorship of a low-stiffness extensively porous-coated femoral stem at 10 years.

UNLABELLED: A novel low-stiffness extensively porous-coated total hip femoral component was designed to achieve stable skeletal fixation, structural durability, and reduced periprosthetic femoral stress shielding. In short- to intermediate-term clinical review, this implant achieved secure biologic fixation and preserved periprosthetic bone. We retrospectively reviewed all 102 prospectively followed patients (106 implants) with this implant to document the longer-term implant survivorship, clinical function, fixation quality, and periprosthetic bone preservation. Ninety-seven patients with 101 implants had current followup or were followed to patient death (range, 1-14 years; average, 10 years). Eighty-six living patients were followed for an average implant survivorship of 10 years. There were no known femoral implant removals. The average Harris hip score at 10-year followup was 98. Radiographs demonstrated secure implant fixation and maintenance of periprosthetic bone. These data suggest this implant design provided long-term function characterized by extensive fixation, structural durability, and radiographic appearance of maintained periprosthetic cortical thickness and density. LEVEL OF EVIDENCE: Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The long-term results of a metal-backed mobile bearing patella.

UNLABELLED: Enthusiasm for metal-backed patella has waned because of the high incidence of complications. Considering that perhaps all metal-backed patellae may not be the same, 256 primary consecutive metal-backed mobile bearing TKAs done between May 1985 and January 1989 were retrospectively reviewed to evaluate the results of a unique mobile bearing metal-backed patella. There were four complications (1.6%). Three patella were revised for polyethylene complications and one well-functioning component was removed at the time of revision of the tibial polyethylene to facilitate range of motion and wound closure. No patella was revised for loosening, subluxation, or dislocation. Our results show that all metal-backed patella are not the same and that compared with the high incidence of failure of fixed bearing metal-backed patellae, the use of the anatomic mobile bearing metal-backed patella can produce excellent, durable long-term clinical and radiographic results with a low incidence (1.6%) of complications. Life table survivorship using revision for any reason as the end point was 97% (95% confidence interval, 93%-100%) at a maximum of 19 years. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series--no, or historical control group). See the Guidelines for Authors for a complete description of levels of evidence.

Liquid gentamicin in bone cement: a laboratory study of a potentially more cost-effective cement spacer.

BACKGROUND: Liquid gentamicin is approved by the Food and Drug Administration, is readily available, and is much less costly than tobramycin, the more commonly used antibiotic in cement spacers. The purpose of the present study was to test the mechanical properties, elution characteristics, and antibacterial activity of liquid gentamicin in an acrylic bone cement spacer. METHODS: Standardized specimens consisting of Palacos cement combined with liquid gentamicin, powdered tobramycin, or no antibiotic were fashioned, and the three groups were tested with regard to compressive and tensile strength, elution characteristics (with use of radioimmunoassays), and antibacterial activity (with use of bioassays). RESULTS: The ultimate compression strength decreased by 49% (from 64.65 +/- 3.89 MPa to 32.96 +/- 3.33 MPa) and the ultimate tension strength decreased by 46% (from 35.85 +/- 2.97 MPa to 19.20 +/- 0.36 MPa) when the specimens containing 480 mg of liquid gentamicin were compared with the controls. The addition of tobramycin had no significant effect compared with the controls. The majority of gentamicin was released from the cement during the initial twenty-four hours (mean concentration, 26.4 mcg/mL). The mean concentrations at three and six weeks were 4.15 and 0.65 mcg/mL, respectively. The bioassays confirmed the bactericidal activity of the gentamicin released from the cement. CONCLUSIONS: Liquid gentamicin in bone cement is potent and bactericidal. Although the mechanical properties of the cement are significantly diminished by the addition of liquid gentamicin, the temporary nature of the cement spacer makes its use potentially worthwhile given the substantial cost savings to the hospital and the patient.

The mini-incision approach to total hip arthroplasty.

Total hip arthroplasty (THA) usually involves an incision of approximately 20 to 25 cm long. Surgeons recently have begun to question the need for such a long incision and are developing less invasive approaches to THA. A mini-incision approach to THA promotes shorter hospital stays, faster rehabilitation, and an increase in patient satisfaction without a detrimental effect on outcome. The surgical technique is based on the classic Moore approach to the hip. The incisions measure 6 to 10 cm in length, and the surgery involves significantly less deep soft-tissue disruption. All the basic tenets of THA are respected and visualization is maintained throughout the procedure for proper placement of the components. Mini-incision THA offers a safe and effective alternative to THA performed through a larger incision. Obese patients typically are not good candidates. Patients with severe hip dysplasia or those undergoing revision surgery require a wider exposure to perform the arthroplasty to ensure the best possible result. In properly selected patients, however, THA can be performed through an abridged mini-incision without compromising the results or exposing the patient to additional risk.

Minimally invasive total hip arthroplasty: the Hospital for Special Surgery experience.

The mini-incision technique is not a radically new technique. The surgeon familiar with the posterior approach will immediately appreciate the inherent similarities. The technique can be developed on a graduated basis by individual surgeons. The surgeon should begin by documenting the length of his or her current routine incision, and then the incision can be progressively reduced in length at a rate that is comfortable. At no time is it necessary to compromise the goals of the procedure because of inadequate visualization. The mini-incision is not for every patient. Obese individuals (BMI> 30), patients with very muscular thighs, stiff hips, or severe deformity may not be candidates for an 8-cm incision, but familiarity with this technique allows even these patients to be operated on through a smaller incision than the traditional 20-25 cm. The initial drive for shorter incisions was a result of patient concerns regarding the cosmesis of the scars and the desire for a more rapid recovery. Subsequent development of the technique and clinical analysis over the last 7 years has shown that THA can be performed safely and effectively through a mini-incision in most patients. So far the author shave found no increased risk for intraoperative or postoperative complications and no problems with component malposition. Longer follow-up is required to determine the long-term outcome; however, in the short term, patients have less blood loss, shorter operative times, and a reduced incidence of limp and cane use at 6 weeks.

Transforming growth factor-beta in calcium alginate beads for the treatment of articular cartilage defects in the rabbit.

PURPOSE: Articular cartilage has only limited capability for intrinsic repair. The use of growth factors has been suggested to improve the repair of cartilage after injury. Reliable delivery systems for these agents are needed. In this study we tested calcium alginate for the delivery of TGF-beta in the treatment of osteochondral defects in the rabbit knee. TYPE OF STUDY: Randomized trial animal study and basic science study. METHODS: In vitro, to establish the kinetics of TGF-beta release from the alginate, 125I- labeled TGF-beta was suspended in 1.2% sodium alginate at concentrations of 1 microg/mL and 10 microg/mL. Beads were formed from 50 microL aliquots and placed into standard culture medium by immersion in calcium chloride solution and incubated at 37 degrees C. A gamma counter was used to measure the amount of TGF-beta that was released into the medium at various time points. In vivo, osteochondral defects were created in the trochlear grooves of 32 New Zealand White rabbits. Defects were treated with plain alginate or with alginate containing TGF-beta at 20 ng/mL or 2,000 ng/mL. Untreated defects served as a control. Animals were killed after 6 and 12 weeks. Knee joints were evaluated grossly with a 12-point grading scale. Histologic sections of the repair tissue were stained with Safranin O and evaluated using a 24-point grading scale by 2 independent blinded observers. Mean scores and standard deviations were calculated. P values were determined using the Student t test. RESULTS: The TGF-beta was released at a surprisingly slow but steady rate. Release rates extrapolated from the gamma counter measurements were 0.25% per hour and 0.33% per hour, for the 1 microg/mL and 10 microg/mL beads, respectively. Gross analysis scores at 6 and 12 weeks resulted in higher scores for both TGF-beta groups without reaching statistical significance. The lower TGF-beta concentration reached the highest scores, whereas the higher concentration (2,000 ng/mL) resulted in increased osteophyte formation. Histologic analysis at 6 weeks resulted in average scores ranging from 14.5 for empty defects and 18.1 for alginate-treated defects, to 20.0 and 20.3 for the 2,000 ng/mL and 20 ng/mL TGF-beta groups, respectively (P <.05). At 12 weeks, histologic scores ranged from 14.9 for empty and 14.5 for alginate to 20.1 and 20.5 for the 2,000 ng/mL and 20 ng/mL TGF-beta groups, respectively (P <.05). These results indicate a significant improvement of the quality of the repair tissue at 6 and 12 weeks with TFG-beta treatment, especially at the lower concentration. CONCLUSIONS: The use of alginate allows the controlled delivery of TGF-beta selectively to the site of injury, potentially avoiding systemic side effects. Furthermore, treatment with TGF-beta appears to improve the repair of articular cartilage defects. Longer-term studies are needed to assess whether the benefits of the TGF-beta treatment can be sustained.